Author Topic: Wood hoist gantry question.  (Read 3201 times)

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Offline Terry Peterson

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Wood hoist gantry question.
« on: June 04, 2012, 08:45:23 AM »
Anyone have any experience using wood to build a hoist gantry?  I am getting older and have some health issues that give me concern when I pick up and hold heavy things, like my half of the boat when I want to turn it over for maintenence or if I build the newer bigger one I want to.  I am talking about building a wooden gantry that is on rollers that could straddle the boat under construction when turning was needed and then be rolled out of the way when not needed.  This link should give an idea of what I am talking about: http://www.northerntool.com/shop/tools/product_200349918_200349918.

I was thinking 4"x4" side posts with a 10' wood beam made from 2 - 2"x8" with plywood glued and bolted inbetween the 2x8's.  I just want 1 tone hoist capacity and am wondering if the described beam would handle the weight or if I needed something more robust?  An 8" aluminum I beam will handle the load but I wanted to stay with wood since I already have the materials laying around the shop.
aargh Matey!

Offline Paul Riccelli PE,NA

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Re: Wood hoist gantry question.
« Reply #1 on: June 04, 2012, 09:06:32 AM »
I've built quite a few over the years and it's fairly easy, but you do have to consider the loads and where on the beam they'll be. I'd skip the aluminum beam all together and just use wood. Aluminum flexes way too much, though it is light.

I usually make box beams for the side posts, rather then a single length of wood, as they're stronger. I'd also do a 4 legged of "A" frame sided thing, instead of a inverted "T" side leg too. Steel is a handy material for these things if you have some welding skills.

If it was me, I'd make an 8" or 10" wooden "I" beam as the cross piece. A 2x8 or 2x10 center (web) and 2x4 flanges on each side. This is incredibly stiff and strong. It's stronger if the 2x8 is rabbited slightly into the 2x4's (1/4 to 3/8" deep groove), naturally all glued and screwed together. The legs I'd make from more of the same, except they don't need to be an "I" beam, just triangulated together ("A" frame style).

The wider the gantry, the bigger the cross beam needs to be. The major issues with gantries are wracking, meaning it might want to lean one way or the other, depending on how stout the legs are. Gussets at the top of the legs, to the cross beam help, but make them big. Making it roll around is another problem, requiring it to be even stiffer. If just for turning a hull, some 2x8 A frame legs, 3/4" plywood gussets and the wooden I beam will do. If wanting to roll around the boat too, then you should tie the two A frames together at the bottom and the cross beam. Get wheels big enough to handle (each) the full load with a 20% safety margin. The bigger the diameter of the wheel, the easier it is to roll around too.

Offline Dave Blake

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Re: Wood hoist gantry question.
« Reply #2 on: June 04, 2012, 02:49:34 PM »
Paul:  Can you whip up a quick sketch of the gantry plan with dimensions?  I'd also be interested in potentially building one than could be disassembled for storage between uses.

Dave

Offline Paul Riccelli PE,NA

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Re: Wood hoist gantry question.
« Reply #3 on: June 05, 2012, 12:50:11 AM »
I don't have a sketch handy and I think dimensions would be application specific, meaning some will need wide ones, others tall ones, while others some sort of other variation.

Picture a pair of 2x8 or 2x10 legs, set at about a 30 degree angle, forming an upside down V. Put a cross brace at the big end of the V, which will bear the weight of the gantry. This cross piece is flat on the ground of course. Some big 'ol plywood gussets on each corner of the cross brace (both sides) to hold the legs firmly.

The upper portion of the "A" frame carries the beam. I'd probably just fasten another short 2x8 cross piece, somewhat below the top of the two legs and place the beam on it. Again big hunks of plywood as gussets to keep things stiff and square.

The beam is just a wooden "I" beam. A 2x8 (or bigger) on edge, with a 2x4 on the flat along the top and bottom edge, making a big wooden I beam. This is what is gusseted to the two sets of A frame legs. The gussets are key, if you want a stable gantry, so go big, as you can always cut them back a little if you have to.

Disassembly is as simple as removing the fasteners, though this means it will probably not be quite as stiff as one never intended to be taken apart (typical of most disassembling things). It could break down into the three basic pieces: the leg frames and the beam.

As to wheels, well this adds a whole new twist to the mix and the lower cross brace will need to be very stiff, so it should probably be boxed or possibly more wooden I beam work. This is because the loads will all be transmitted through the small contact patch, where the wheel touches the ground and you'll pick up a bunch of cantilever and other additional strains in the structure.

Offline Paul Riccelli PE,NA

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Re: Wood hoist gantry question.
« Reply #4 on: June 07, 2012, 12:27:47 AM »
This should give you an idea of what I'm talking about. You can see the "I" beam, though not resting on the upper cross piece, nor gusseted in. Rough scale for this is 8' tall 2x8's. This can easily handle a Weekender roll over, though 4 or 5 well fed friends can roll a Weekender pretty easily too. A Vacationer builder might want to upgrade to 2x10's or 2x12's. I've lifted two tons with doubled up 2x12's previously.
« Last Edit: June 07, 2012, 12:31:34 AM by Paul Riccelli PE,NA »

Offline Dave Blake

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Re: Wood hoist gantry question.
« Reply #5 on: June 07, 2012, 11:20:08 AM »
Thanks, Paul.

Offline John Anderman

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Re: Wood hoist gantry question.
« Reply #6 on: June 07, 2012, 10:12:06 PM »
Boy do you guys make me feel like a redneck, I rolled my Vacationer over with a tow strap, a 50' rope, and my minivan! I eased her up to the tipping point, then had the wife steady the the bow while I lowered the boat by hand. It's amazing how light these hulls are!
Vessels of freedom, harbors of healing....boats

Offline Dave Blake

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Re: Wood hoist gantry question.
« Reply #7 on: June 08, 2012, 06:03:29 AM »
John:  When I flipped my Weekender we did it by hand: 4 guys to do the heavy lifting and 2 women to steady and guide her. It was pretty easy, but require coordinated manpower.  I like the gantry idea, especially when working alone on small bottom repairs, etc. so you don't have to prepare a tub of cold beer and a barbecue every time you need help!

Dave

Offline Paul Riccelli PE,NA

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Re: Wood hoist gantry question.
« Reply #8 on: June 08, 2012, 11:54:41 AM »
A gantry is really handy once you've completed the boat and need to work on the bottom or keel. Snatching it off a trailer can be troublesome without one. I'm a big tree guy, having many huge live oaks in the yard, most of which just seem to have grown limbs intended to drop a chain fall or come-along from. Several trees in my yard have a loop of chain around the best branches, just waiting until I need to hook something to them. Works great for yanking engines out of stuff too.

Offline Terry Peterson

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Re: Wood hoist gantry question.
« Reply #9 on: June 08, 2012, 01:02:49 PM »
I am a big sized fella.  6'1" 300 pounds.  I use to be able to put a full 55 gallon drum in the back of a pickup by myself.  There is a trick to it but you still have to be fairly strong since you are moving 500+ pounds.  That was 40 years and a good heart ago.  Now days I am still big but getting weaker by the month.   The same boat I use to move around by myself, its only about 260 total weight, I need help turning these days.  Given I am a year older then the doctors told me I would ever be I accept that there are more limitations then there use to be and take it easier these days.

I want to build a bit bigger boat, about 20 feet maybe without the nose stick so will probably build two gantries and use then fore and aft when I want to roll the hull.  I will also try and build some of the super structures separate from the boat and then hoist them up, over and down in.  I am not sure on that small a boat if there will be that many opportunites for such but it is an idea.  Adding an inboard is part of that dream and a hoist would make that ever so much easier.  At this point it is all just dreams but they don't cost much and I will need to flip the smaller boat at least twiced a year as well as move it off the trailer so the gantry hoist idea has merit.

I have a lean to attached along one side of the shop that is currently used to hold lumber and ply left overs or boards that were to good to leave on the stack at the local yard.  I am thinking of putting in 3 sky hooks and hanging the small boat in the lean to during the off season or if I get a second smaller boat and need the trailer for that one.  The boat I built is wide and slow.  Perfect for me but if I know my kid she will want something faster that requires hiking out and all the athletic things that go against drinking a beverage while chasing mermaids on a light wind afternoon.
aargh Matey!

Offline Al Stead

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Re: Wood hoist gantry question.
« Reply #10 on: June 08, 2012, 06:18:41 PM »
Many years ago I bought a set of high lift camper jacks.  I bought them to lift my heavy dog box off the pickup frame for repair and maintainence.  Now I use them for lifting the boat off the trailer or  building cradle.  Mostly however, I use them to steady the stern of the boat when I have to get up on or in it when it is sitting on the trailer.  I have a tongue jack that I use to roll it around and with the camper jacks snugged up under the rub rails I have a three point solid srtance that is safe and won't mar the finish.  I can't roll the boat over with them, but I can do pretty much anything else. 

Al

Offline Paul Riccelli PE,NA

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Re: Wood hoist gantry question.
« Reply #11 on: June 08, 2012, 10:44:32 PM »
For those of you that have some cash lieing around with nothing better to do, you can get manual, electric and hydraulic lifts and gantries fairly cheaply. You'll find automotive style lifts and rolling gantries at auctions and the manual ones can be had pretty inexpensively from Harbor Freight. The Harbor Freight unit is about $700 bucks, rated at 2,000 lbs., about 8' between the legs and adjusts from 8' to, nearly 13' tall. The small I beam on top is the limiting factor, which could be reinforced easily enough for more weight.

I'm a build it myself kind of guy, so unless I find a used one cheap, I'll make something that suits my needs best.